1. Field of the Invention
This invention pertains to urinary bladder catheters and more particularly to drainage type catheters incorporating retaining means.
2. Prior Art
Ideally, all drainage type urinary bladder catheters should effect complete drainage from the bladder cavity. The design of many prior art bladder catheters has, however, resulted in the accumulation of a urine pool in the bladder near its junction with the urethra. As is well known, the accumulation of such a urine pool could result in infection or even crystallization. Consequently, those prior art catheters which do not solve this problem are disadvantageous.
Bladder catheters have been designed with means for enlarging the drainage apertures or slits once the catheter has been inserted in the bladder. Upon being widened, these apertures or slits provide enhanced drainage thus avoiding the accumulation of a urine pool. Prior art catheters of this type have, however, had certain deficiencies.
Thus, U.S. Pat. No. 3,397,699 issued to Kohl discloses a flexible catheter having a plurality of longitudinal slits in a zone adjacent the distal end of the catheter. The slits define a plurality of foldable wings which are biased to radially outwardly extending positions and the portions of the catheter above and below the slits are joined together by resilient elements. In use, a stylet is inserted through the catheter lumen until the distal end thereof engages the distal end of the catheter. Sufficient force is then exerted on the distal end of the catheter through the stylet to push the portion of the catheter above the slits as far as possible from the portion below. The elastic elements are thereby stretched causing the wings to move to a position wherein they form a smooth continuation with the unslitted portions of the catheter. The catheter is then introduced into the bladder until the wings clear the interior wall thereof, whereupon the proximal end is held against movement while the stylet is gradually withdrawn. As the elastic elements retract the wings return to their outwardly extending positions and engage the bladder wall thereby retaining the catheter in the bladder. Effective drainage is accommodated through the slits which are enlarged when the wings are in their outwardly extended positions.
Kohl's catheter is disadvantageous insofar as it requires the use of a stylet or other means to stretch the elastic elements and move the wings to a flattened position to allow insertion and withdrawal of the catheter. Moreover, since the elastic elements extend longitudinally through the catheter lumen, they may interfere with the stylet during insertion and removal thereof.
U.S. Pat. No. 3,815,608 issued to Spinosa et al. discloses a bladder catheter similar to Kohl's. Thus, the wings are pretreated to assume a natural position in which they project outwardly from the body of the catheter. However, rather than employing elastic elements, Spinosa employs individual drawstrings, one for each wing, which extend through the lumen and are secured directly to the midpoints of the wings. Thus, by pulling the strings toward the proximal end, the wings are flexed to a flattened position. While this embodiment obviates the necessity of employing a stylet to effect insertion and withdrawal, the bundle of strings which extends through the lumen of the catheter may eventually interfere with effective drainage, especially with extended use. Additionally, Spinosa's catheter relies solely on the resiliency of the wings to return them to the outwardly extended positions. In the event complete return is not effected, drainage will be reduced since the spaces between the wings will be smaller, and in the extreme situation, accidental catheter withdrawal may occur.
U.S. Pat. No. 2,649,092 issued to Wallace also discloses a catheter having a plurality of longitudinally extending slits adjacent the distal end which define wings therebetween. The wings, however, are biased in a flattened position and project outwardly upon retraction of the distal end relative to the proximal end. Like Spinosa's catheter, the catheter disclosed by Wallace is disadvantageous since it relies solely on the resiliency of the material comprising the wings to return the wings to the flattened position to effect catheter removal. Complete return is highly unlikely, especially after the wings have remained in the flexed position for an extended period of time, as is often the case with catheters employed for bladder drainage. Upon failure of the wings to return completely to their unflexed position, removal of the catheter becomes extremely painful as the wings may abraid the internal walls of the urethra and the bladder.
U.S. Pat. No. 3,889,686 issued to Duturbure discloses yet another self retaining bladder catheter in which a flexible membrane extends about the tubular portion of the catheter adjacent the distal end. The tubular member includes two bores, one for the conventional drainage purpose, and the other for introducing a fluid into the flexible membrane whereby the flexible membrane may be expanded once the catheter has been inserted into the bladder. Thus, the membrane serves much the same purpose as the wings in the prior art catheters described above. One major disadvantage of this catheter is that except for a small aperture below the membrane closely adjacent the internal wall of the bladder, no other drainage ports are provided or could be provided between that point and the distal end of the membrane. Clearly, this reduces drainage and may result in the accumulation of a urine pool. Of course, the catheter may be provided with additional drainage ports located distally of the membrane. Such additional ports, however, would not enhance drainage from the portion of the bladder cavity below the distal end of the membrane. Moreover, should the aperture beneath the membrane become occluded, drainage from this portion of the bladder could be blocked altogether. Additionally, the necessity of providing two non-communicating bores in the tubular member and the introduction of a suitable fluid to expand the membrane increase both the cost and complexity of this catheter thereby reducing its commercialability.
U.S. Pat. No. 3,490,457 issued to Petersen discloses a catheter which employs a sleeve having circumferentially spaced longitudinally extending slits which sleeve is disposable about a central tubular member to provide outwardly extending wings for engaging the internal wall of the bladder and retaining the catheter therein. This catheter, however, requires the use of an obturator or stylet to effect insertion of the catheter. Moreover, Petersen's catheter, like Wallace's, relies solely on the natural resiliency of the sleeve material to return the wings to their unflexed position.
Lastly, U.S. Pat. No. 3,692,029 issued to Adair discloses a catheter wherein a compression spring disposed distally of the wings biases the wings into an outwardly extended position. A stylet is insertable through the lumen of the catheter to compress the spring and flatten the wings. Thus, this catheter is disadvantageous insofar as it requires the use of a stylet to effect insertion and withdrawal. Moreover, because the wings normally are biased in the outwardly extended position, pressure must be continuously applied to the stylet during both insertion and withdrawal to prevent internal damage to the patient.